The present invention relates to an albedo dosimeter encapsulation for measuring neutron and gamma radiation, the arrangement having at least two dosimeter zones.
Neutron dosage measurements are preferably made by means of albedo dosimeters which include TLD (thermoluminescence dosimeter) detectors that record gamma radiation and neutrons in the same manner. The measured neutron values are separated, for example, by means of .sup.6 LiF and .sup.7 LiF dosimeter pairs which have the same gamma sensitivity but different neutron sensitivities. The detection of thermal neutrons is here made by way of a nuclear reaction .sup.6 Li(n,.alpha.).sup.3 H. The difference in measured values of such pairs of TLD dosimeters is thus proportional to the neutron fluency of thermal neutrons: EQU .alpha.=.alpha.(.sup.6 LiF)-.alpha.(.sup.7 LiF)
An albedo dosimeter is a dosimeter encapsulation of a cadmium or of a boron containing plastic in which is disposed a pair of dosimeters or a combination of TLD detectors. The Hankins single dosimeter (Hankins, D. E. Reports LA-5261 (1973)) comprises a pair of dosimeters in the center of a polyethylene moderator which is encased on all sides by cadmium. The Karlsruhe albedo neutron dosimeter (Piesch et al, Proc. Int. Conf. of Luminescence Dosimetry, Krakow (1974), p. 1201) includes three pairs of dosimeters, with the values measured from two pairs of dosimeters m and a, in addition to the albedo dosimeter i, providing the values for the analysis of the neutron spectrum and thus for the determination of the locus dependent calibration factor for the albedo dosimeter i.
The advantage of the single dosimeter is the negligible influence of the distance between the dosimeter and the body of the person carrying the dosimeter. A drawback of the single dosimeter is an error in the dosage determination up to a factor of 20. In comparison therewith, the Karlsruhe albedo dosimeter is able to determine the neutron equivalent dose in a given scattered radiation field to .+-.25%. Body contact, i.e. the wearing of a dosimeter belt, however, is required for the Karlsruhe albedo dosimeter. Other advantages of the Karlsruhe albedo dosimeter result from the possibility of analyzing the neutron radiation field during phanthom calibration with a single sphere albedo measuring technique, and of obtaining the measured data relating to the scattered neutron radiation field immediately after examination of the dosimeters by means of an on-line computer program (Piesch et al, Nucl. Instr. Meth. 175 (1980) pages 180 to 182). The drawback here is the cumbersome insertion and removal of the detectors into and out of the encapsulation.